Preheat oven to 400F. Cut 3 of the green bell peppers in half lengthwise. Cut out and remove the stem and seeds.
3 large green bell peppers
Place bell pepper halves cut side up in the baking dish. Spray the insides with a bit of cooking spray (or brush with olive oil) and season with kosher salt. Transfer to the oven and bake for about 20 minutes. If any liquid is pooling in the bell peppers after you take them out of the oven, carefully use tongs to drain it off.
cooking spray, kosher salt
Meanwhile, bring a large pan to medium heat. Once it's hot, add half of the avocado oil (1 tbsp). Then, add sliced bell peppers and onion. Season with kosher salt & black pepper. Sauté, stirring occasionally, for about 8 minutes or until mostly tender.
2 tbsp avocado oil, 1 small red bell pepper, 1 small green bell pepper, 1 small yellow onion, kosher salt & black pepper
Then, add garlic and red pepper flakes. Stir and let cook for 1 more minute. Remove from the pan.
red pepper flakes, 3 garlic cloves
Increase heat to medium-high. Then, add the remaining 1 tbsp of avocado oil. Once hot, add the thinly sliced steak and spread out in the pan so there's minimal overlap. Season with kosher salt & black pepper. Let cook for 1-2 minutes per side, or until there's no more pink.
2 tbsp avocado oil, 1 ¼ lbs petite sirloin steak, kosher salt & black pepper
Turn off the heat. Drain off any excess liquid from the pan. Then, add back in the sautéed bell peppers and onions and stir until everything is combined.
Add a generous amount of the philly cheesesteak mixture to the par-cooked bell peppers. Then, top each with a slice of provolone. Transfer back to the oven to bake for 10 minutes, or until the cheesy is melted.
6 slices provolone cheese
Optionally, top with some chopped parsley and fresh cracked black pepper. Enjoy!